The objective of the research program is to provide information on the functioning and maintenance of the vertebrate photoreceptor. The program emphasizes the mechanism of action of the rod visual pigment, rhodopsin, in the visual process. In providing basic information on the functioning of the vertebrate photoreceptor, the program may also indicate the basis of operation of other receptors such as osmotic receptors (for blood pressure), pH receptors (for oxygen levels), pain, etc. and other sensory receptors such as hearing, taste, etc. A number of experimental approaches are used to obtain the data. Excised vertebrate retinas, or whole animal or excised eyes from fruitflies, and solution extracts of the visual pigment, are used. Intracellular recording with perfusion, extracellular recording with perfusion, measurements of respiration, microspectrophotometry, regular spectrophotometry and disc gel electrophoresis are some of the methods used to obtain the data.